There have been approaches in the art for providing a region at the surface of a solar cell which provides minimum attenuation of the photons of light while at the same time improving the situation involving the "Fermi Level Pinning" phenomenon. One example of such an approach is U.S. Pat. No. 3,675,026 in which a p-type layer of gallium aluminum arsenide covers the p-n gallium arsenide device and reduces losses by providing a lattice-matched expitaxial layer.
Heretofore in the art, however, there has been a limitation to such structures in that the layers themselves have a tendency to absorb some of the solar photons that have energies that are higher than the bandgap of the particular cover layer.